netdev - Re: [PATCH bpf-next 2/2] samples: bpf: get ifindex from ifname

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Message-ID: <CAGnkfhxGgfoUb9zxVBaAZ4pcOXhMa7e1hFmkJ8_BG=+mUsSUQQ@mail.gmail.com>
Date:   Fri, 19 Oct 2018 08:42:22 +0000
From:   Matteo Croce <mcroce@...hat.com>
To:     ys114321@...il.com
Cc:     netdev <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH bpf-next 2/2] samples: bpf: get ifindex from ifname

On Fri, Oct 19, 2018 at 5:35 AM Y Song <ys114321@...il.com> wrote:
>
> On Thu, Oct 18, 2018 at 1:48 PM Matteo Croce <mcroce@...hat.com> wrote:
> >
> > Find the ifindex via ioctl(SIOCGIFINDEX) instead of requiring the
> > numeric ifindex.
>
> Maybe use if_nametoindex which is simpler?
>
> >
> > Signed-off-by: Matteo Croce <mcroce@...hat.com>
> > ---
> >  samples/bpf/xdp1_user.c | 26 ++++++++++++++++++++++++--
> >  1 file changed, 24 insertions(+), 2 deletions(-)
> >
> > diff --git a/samples/bpf/xdp1_user.c b/samples/bpf/xdp1_user.c
> > index 4f3d824fc044..a1d0c5dcee9c 100644
> > --- a/samples/bpf/xdp1_user.c
> > +++ b/samples/bpf/xdp1_user.c
> > @@ -15,6 +15,9 @@
> >  #include <unistd.h>
> >  #include <libgen.h>
> >  #include <sys/resource.h>
> > +#include <sys/ioctl.h>
> > +#include <sys/socket.h>
> > +#include <linux/if.h>
> >
> >  #include "bpf_util.h"
> >  #include "bpf/bpf.h"
> > @@ -59,7 +62,7 @@ static void poll_stats(int map_fd, int interval)
> >  static void usage(const char *prog)
> >  {
> >         fprintf(stderr,
> > -               "usage: %s [OPTS] IFINDEX\n\n"
> > +               "usage: %s [OPTS] IFACE\n\n"
> >                 "OPTS:\n"
> >                 "    -S    use skb-mode\n"
> >                 "    -N    enforce native mode\n",
> > @@ -74,9 +77,11 @@ int main(int argc, char **argv)
> >         };
> >         const char *optstr = "SN";
> >         int prog_fd, map_fd, opt;
> > +       struct ifreq ifr = { 0 };
> >         struct bpf_object *obj;
> >         struct bpf_map *map;
> >         char filename[256];
> > +       int sock;
> >
> >         while ((opt = getopt(argc, argv, optstr)) != -1) {
> >                 switch (opt) {
> > @@ -102,7 +107,24 @@ int main(int argc, char **argv)
> >                 return 1;
> >         }
> >
> > -       ifindex = strtoul(argv[optind], NULL, 0);
> > +       sock = socket(AF_UNIX, SOCK_DGRAM, 0);
> > +       if (sock == -1) {
> > +               perror("socket");
> > +               return 1;
> > +       }
> > +
> > +       if (strlen(argv[optind]) >= IFNAMSIZ) {
> > +               printf("invalid ifname '%s'\n", argv[optind]);
> > +               return 1;
> > +       }
> > +
> > +       strcpy(ifr.ifr_name, argv[optind]);
> > +       if (ioctl(sock, SIOCGIFINDEX, &ifr) < 0) {
> > +               perror("SIOCGIFINDEX");
> > +               return 1;
> > +       }
> > +       close(sock);
> > +       ifindex = ifr.ifr_ifindex;
> >
> >         snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
> >         prog_load_attr.file = filename;
> > --
> > 2.19.1
> >

Right, even better. Will do a v2, thanks.

-- 
Matteo Croce
per aspera ad upstream